The number of people illegally crossing into Europe dropped last year to its lowest level in five years -- but there's been a spike in the number reaching Spain, figures show.

An estimated 150,000 people entered the European Union through irregular crossings in 2018, border and coastguard agency Frontex said Friday. That represents the lowest total since 2013 and is 92% below the peak recorded during the migration crisis in 2015.

The drop was due to a dramatic fall in the number of migrants taking the central Mediterranean route from Libya, Algeria or Tunisia to Italy, Frontex said. A little over 23,000 irregular crossings were detected on this route for the year, an 80% decrease compared to 2017.

Meanwhile, the number of arrivals in Spain via the western Mediterranean route, leaving from Morocco, doubled last year for the second year in a row to 57,000. Most of the migrants on this route originated from countries in sub-Saharan Africa, although the number of Moroccans has increased in recent months, Frontex said. Many also came from Guinea, Mali and Algeria. Spain's government has also allowedsome ships carrying rescued migrants to dock in its ports after they were barred entry to Italy or Malta.

Afghan, Syrian and Iraqi nationals made up the largest number of migrants entering Europe by the eastern Mediterranean route last year, Frontex said, with the total rising by nearly a third to 56,000. This increase was mainly caused by a higher number of migrants crossing the land border between Turkey and Greece, it added, many of them Turkish nationals.